A composition for a fluorinated coating agent such as a coating material, a hard coating agent or a substrate protecting coating fluid, is excellent in the weather resistance and the ultraviolet resistance, and is thereby used in a wide range of high-rise buildings, large-sized structures, ships, vehicles, housing, bridges, etc. as a maintenance-free high performance coating agent.
However, in a hot and humid environment with a large amount of sunlight (amount of ultraviolet light), a coating film is deteriorated from such reasons that a large quantity of radical species are generated from a pigment such as a titanium oxide pigment.
A fluorinated resin coating material is a coating material in which a fluoropolymer is blended. The fluororesin coating material has excellent performance in the weather resistance, etc. as compared with a universal resin coating material in which an acrylic resin, a polyester resin, an alkyd resin or the like is blended. However, in order to further increase the stain resistance of the fluororesin coating material and the hardness of the coating film, one having a crosslinked moiety is used as a fluoropolymer, and a curing agent of an aminoplast resin type such as a polyvalent isocyanate compound or a methylated melamine resin is blended. With respect to a coating film obtained from a fluororesin coating material comprising a polyvalent isocyanate compound as a curing agent, the crosslinking manner is urethane crosslinking. However, since the bond energy of the urethane bond is low, the coating film is deteriorated at an early stage under severe conditions.
Further, the following method has been disclosed, in which an alkoxysilane compound or a hydrolysed condensate thereof is blended as a curing agent with the above fluororesin coating material to improve the weather resistance of a coating film.
A fluororesin coating material having an alkoxysilane as a curing agent blended with a fluorocopolymer having no hydrolysable silyl group and having a hydroxy group and an acid radical (Patent Document 1).
A fluororesin coating material having a hydrolysed condensate of tetramethoxysilane blended with a fluorocopolymer essentially containing monomer units based on a fluoroolefin and polymerized units of a monomer having a hydrolysable silyl group directly bonded to e.g. a vinyl group, an allyl group, a butenyl group, a vinyloxy group, an allyloxy group, a (meth)acryloyl group, CH2═CHO(CH2)3—, CH2═CHCOO(CH2)3—, CH2═CHOCO(CH2)3—, CH2═C(CH3)COO(CH2)3— or CH2═C(CH3)COO(CH2)2—O—(CH2)3— (Patent Document 2). Further, it is disclosed that it is preferred to incorporate monomer units based on a (meth)acrylate in the fluorocopolymer in view of solubility in an organic solvent and flexibility of a crosslinked coating film.
A resin composition for a moisture-curable coating material, which has a fluorocopolymer having alkoxy groups introduced to side chains by reacting a fluorocopolymer having hydroxy groups in side chains with an isocyanate functional silane, and an organopolysiloxane having at least two silanol groups or alkoxysilyl groups in one molecule, blended (Patent Document 3).
Patent Document 1: JP-A-4-275379
Patent Document 2: JP-A-2000-212501
Patent Document 3: JP-A-63-30571